This invention relates to a binder apparatus, and, more particularly, to a clamping device or holder for supporting large paper pads and the like.
Holders for large paper pads used in lectures, presentations and other displays are wellknown. Such holders generally comprise a back support member having a plurality of spaced pins or pegs which is adapted to be mounted to an upright support or stand. The pins are insertable within holes formed along one edge of the paper pad for hanging the pad on the back support member, and, in turn, the upright stand. In order to prevent the papers from becoming dislodged from the pins, prior art paper pad holders also include an elongated clamping member pivotally connected to the back support member along a longitudinally extending edge. The clamping member is pivotal between a closed clamping position wherein it overlies the pins and clamps the paper pad in place, and an open position which uncovers the pins and permits the pad to be removed.
In many prior art paper pad holders, movement of the clamping member between the open and closed position is assisted by a spring device connected between the clamping member and back support member. In some pad holders, conventional coil springs are connected between the back support and clamping member to resiliently urge the clamping member in either a closed position against the paper pad or an open position. The coil springs are generally disposed within enlarged recesses formed in the clamping member which are often fully exposed in the open position of the clamping member. This detracts from the appearance of the sheet holder. In addition, the recesses tend to collect dirt which restricts full deflection of the springs and falls out onto the sheets of the paper pad.
To overcome the problems created by coil springs, prior art sheet holders have employed elongated springs having longitudinal edges connected to mating longitudinal grooves formed on the exterior of the clamping member and back support member. Conventionally, such prior art springs are formed of spring steel. In order to fabricate the springs from spring steel, the spring steel is first cut to width, shaped in the desired cross section by a roll former fixtured with the appropriate dies and then heat treated to obtain the proper hardness. The fabrication process, and particularly the forming dies, are relatively expensive which adds greatly to the cost of the paper pad holder.